The present invention relates to objects such as documents and the like which have colored areas thereon that area difficult or impossible to reproduce using known color photocopiers or color photography wherein the photosensitive emulsions or materials used in the photocopiers or photography are sensitive both to reflections from the visible light wavelength range for humans and ranges adjacent thereto.
The recently developed technology for reproduction of colored pattern which utilizes sensitive emulsion or material, such as color photography and color copiers, is capable of reproducing patterns in a color which appears to be identical to that of the original. A potential undesirable application of this convenient technology is in unauthorized and criminal reproduction of valuable documents or color objects. Particularly when it is utilized for reproduction of paper money, stock certificates, bond certificates, stamps, checks, drafts, bills of lading, letters of guarantee, credit cards, various certificates, various coupons, various slips, and/or the objects with such nature, and if the reproductions of such objects should circulate in the market place or through various transactions, it would evidently cause disturbances in economic and financial activities, and would be serious enough to require action to maintain social justice.
Included in the means available in the prior art which are applicable for prevention of forgery of such objects of value are:
(1) The employment of particular kinds of paper such as paper having watermarks;
(2) Utilization of particular patterns such as fine, minute and/or complicated background camouflages or ground designs and hidden marks;
(3) Utilization of a particular process for representation of patterns such as mandatory employment of particular and sophisticated engraving machines for the production of plates;
(4) Employment of a particular, sophisticated and expensive printing process such as Sammel druck machines; and
Each of these means is inevitably accompanied by cost disadvantages. In addition, the recent development in the aforementioned technology for reproduction of colored patterns which is excellent in performance and simple in handling operation, has added another disadvantage to these conventional means for the prevention of reproduction. When a colored object is reproduced either directly with such color reproduction technology or indirectly with such technology which is utilized for production of blocks or plates with which printing will be made, some magnitude of discrepancy would be recognized between an original and the reproduction from the viewpoint of visibility, dimensional distortion of patterns and/or paper quality. Experts however, often have a difficult time identifying a colored object as a reproduction. Particularly, in view of the fact that ordinary transactions are carried out by personnel who are not professional in this technical field and who do not have or use sufficient time for making sure of the validity of paper money, securities and/or documents to be transferred by some means including direct comparison with the genuine piece, it would be unrealistic to assume that the aforementioned color reproduction technology will not be applied to the undesirable purposes of forgery.
Prior art techniques are known for thwarting unauthorized black and white reproductions of patterns which utilize camouflaging or distorting backgrounds and the like. Such prior art teaching is not drawn to color reproductions not to the particular method employed here.